1. Field of the Invention
The present invention relates to a fuel system for an engine powering a small watercraft. In particular, the invention relates to an accelerator pump of a fuel system for such an engine.
2. Description of Related Art
Personal watercraft generally include a water propulsion device which is powered by an internal combustion engine. These watercraft are generally quite small in size, often limited to use by one to three persons. The engine of the watercraft is positioned within an enclosed engine compartment defined by a hull of the watercraft. Due to the small size of the watercraft, the engine compartment is very small, and thus the engine must be arranged in fairly compact fashion.
When of the two-cycle variety, previous engines generally have fuel delivered to incoming air for combustion via one or more carburetors. The carburetor provides a relatively simple mechanism for providing fuel (i.e. it does not require complex electronic controls which may be associated with a fuel injection system) and is relatively reliable.
In many applications, the use of a carburetor having a single fuel supplying mechanism and throttle valve is sufficient. The sporting nature of use associated with personal watercraft makes it very desirable, however, to selectively add a quantity of fuel over and above the basic fuel supplying mechanism. Specifically, when moving a watercraft from idle to its planing speed, rapid acceleration is often desired. For the engine to provide the necessary acceleration, a great deal of fuel must be supplied to the engine in a relatively short time period. This amount of fuel, however, is much larger than that generally required when the engine is idling or when the engine is running at a relatively steady high speed, such as after the watercraft has planed.
As such, the carburetor may be provided with a fuel increasing mechanism or "accelerator pump" arranged to increase fuel supply in certain situations. Often, this mechanism includes a fuel chamber in which a cache of fuel is stored until the necessary delivery time. A problem exists that this fuel cache is often a fuel chamber which is located at the engine and which is subject to the very high heat generated by the engine and trapped in the small engine compartment. The exposure of the fuel cache to these high temperatures contributes to evaporation of the fuel. Since the time between periods of engine acceleration may be quite long, when the need for the supply of extra fuel finally arises, the fuel chamber may be empty or at least depleted.
Other embodiments of accelerator pumps arrange the pump inside the carburetors themselves. This structure often complicates the structure of the carburetor and increases the size of the overall assembled engine. The increased size of the assembled engine is due to the need for each carburetor to have an individual fuel cache.
Thus, a need exists for an improved accelerator pump arrangement for an engine powering a personal watercraft.